I think it's not possible.
In one of my apps I've created second grid under the basic one to display sum..
Everything is ok, when you have enough place on screen to view all columns
Creo que el control grid debe tener la propiedad footer ya que contiene la propiedad header.
En mi POS incluí label y textbox para mostrar información sobre las columnas cantidad y total.
I do like Daniel and suggest for footer Label like Serge, This way you can change value on grid save if needed.
I modified my tbrowse example with this to try, works perfect but have not reposted it yet.